Experiments carried out by the Reproductive Neuroendocrinology Section are focused on the cellular and subcellular mechanisms regulating the release of luteinizing hormone-releasing hormone (LHRH) and other hypothalamic peptides that participate in the modulation of pituitary hormone release. Specific studies are designed to elucidate the role of monoaminergic neurotransmitters in the release of LHRH from nerve terminals, the nature of the specific aminergic receptors involved in the neuronal activation that precedes LHRH release, the clarification of the post-receptor events that participate in the peptide-release process, the involvement of arachidonate metabolites in amplifying the response to key neurotransmitters, and the additional role played by other intracellular messengers such as CA+2 and other putative intracellular messengers derived from the metabolism of membrane phospholipids. Other parts of the project are directed to perform an in-depth analysis in vivo of the changes in monoamine turnover and metabolism in discrete brain nuclei that are known to be involved in regulation of gonadal function. Different experimental paradigms are employed, to re-create situations calling for an enhanced (or altered) function of the hypothalamic-pituitary-gonadal axis, such as steroid-feedback manipulations, pregnancy, lactation, estrous cycle, stress, ablation of selected endocrine glands or brain areas, etc. Finally, a group of experiments are directed to evaluate the mechanisms underlying the effects on the reproductive sphere of neonatal neurotoxin treatment, as well as the developmental changes and the role of steroids on certain sexually dimorphic patterns of gonadotropin secretion. The results are integrated to provide a comprehensive hypothesis of the complex, multi-level regulatory mechanism modulating gonadal function.